graph TD
    Root["Convert food waste to compost"]

    subgraph S1 ["Subsystem 1: Receive waste<br/>(Take in scraps)"]
        A1["Accept waste<br/><i>Hopper with lid</i>"]
        A2["Detect load<br/><i>Weight sensor</i>"]
        A3["Filter odor<br/><i>Carbon filter</i>"]
        A1 --- A2 --- A3
    end

    subgraph S2 ["Subsystem 2: Break down<br/>(Shred and digest)"]
        B1["Shred waste<br/><i>Rotating blades</i>"]
        B2["Mix material<br/><i>Agitator paddles</i>"]
        B3["Add microbes<br/><i>Starter culture</i>"]
        B1 --- B2 --- B3
    end

    subgraph S3 ["Subsystem 3: Set conditions<br/>(Heat, air, moisture)"]
        C1["Heat batch<br/><i>Heater, 55–65 °C</i>"]
        C2["Supply air<br/><i>Fan and vents</i>"]
        C3["Drain excess<br/><i>Moisture tray</i>"]
        C1 --- C2 --- C3
    end

    subgraph S4 ["Subsystem 4: Output compost<br/>(Finish and unload)"]
        D1["Dry compost<br/><i>Final heat cycle</i>"]
        D2["Dispense<br/><i>Removable bin</i>"]
        D3["Guard users<br/><i>Lid interlock</i>"]
        D1 --- D2 --- D3
    end

    Root --> S1
    Root --> S2
    Root --> S3
    Root --> S4